Cristina Batalla García

Extended models for TSALBP with ergonomic risk constraints

In this paper, we present an extension to the TSALB problem (Time and Space constrained Assembly Line Balancing) with ergonomic risk restrictions. This ergonomic risk is defined from the task durations and their categories regarding to the risk factor for the workers. A study is presented through a case linked to an engine assembly line in the Automobile industry, considering variable demand.

GRASP for sequencing mixed models in an assembly line with work overload, useless time and production regularity

A GRASP algorithm is presented for solving a sequencing problem in a mixed-model assembly line. The problem is focused on obtaining a manufacturing sequence that completes the greatest possible amount of required work and fulfils the production regularity property. The implemented GRASP algorithm is compared with other resolution procedures by means of instances from a case study linked to the Nissan’s engine plant in Barcelona.

Solving a Mixed-Model Sequencing Problem with production mix restriction by Bounded Dynamic Programming

In this article, we propose a hybrid procedure based on bounded dynamic programming (BDP) assisted by linear programming to solve the mixed-model sequencing problem with workload minimization (MMSP-W) with serial workstations, free interruption of the operations and with production mix restrictions. We performed a computational experiment with 23 instances related to a case study of the Nissan powertrain plant located in Barcelona. The results of our proposal are compared with those obtained by the Gurobi solver and previous procedures. MSC:90C39, 90B35

LED misalignment determination in LED illumination optics using hole grid pattern distribution

This paper presents a method for determining the degree of misalignment between a LED and its epoxy encapsulation in a simulated environment. The misalignment is determined by analyzing the light emitted by the optoelectronic component and transmitted through a grid of holes. The results obtained are compared with simulated and experimental registers wherein there is no misalignment between the LED and the epoxy but a displacement of the whole optoelectronic component perpendicularly to the observation axis. We prove that the method used allows us to distinguish between the existence of misalignment inside the optoelectronic component and a simple displacement between the optoelectronic component and the observation axis.

Accurate polarimeter with multicapture fitting for plastic lens evaluation

Abstract. Due to their manufacturing process, plastic injection molded lenses do not achieve a constant density throughout their volume. This change of density introduces tensions in the material, inducing local birefringence, which in turn is translated into a variation of the ordinary and extraordinary refractive indices that can be expressed as a retardation phase plane using the Jones matrix notation. The detection and measurement of the value of the retardation of the phase plane are therefore very useful ways to evaluate the quality of plastic lenses. We introduce a polariscopic device to obtain two-dimensional maps of the tension distribution in the bulk of a lens, based on detection of the local birefringence. In addition to a description of the device and the mathematical approach used, a set of initial measurements is presented that confirms the validity of the developed system for the testing of the uniformity of plastic lenses.

Comparative models for minimizing ergonomic risk in assembly lines

We present a new mathematical model for the assembly line balancing problem with the objective of maximizing the line comfort to operators. Besides minimizing discrepancies between the ergonomic risks of workstations, balancing is subject to temporal and spatial conditions for the workstations. To evaluate the performance of the proposed model, we compare it with other mathematical model whose objective is minimizing the maximum ergonomic risk of a mixed-model assembly line. To compare the models, a case study linked to Nissan’s engine plant in Barcelona (NMISA, Nissan Motor Iberica – BCN).

Minimizing lost-work costs in a mixed-model assembly line

Mixed-model assembly lines present two issues due to differences in processing times from product types; these issues are the work overload or unfinished work and the useless time or unproductive time. Within this context, we present, in this paper, a new mathematical model for the mixed-model sequencing problem. This model minimizes the costs by lost production and idle productive time. The model also allows processors carry out their workload with a factor activity greater than the normal, in order to reduce the work overload if it is necessary. Obviously it is also considered to provide economic compensation to workers based on their level of activation. Finally, the model is evaluated by a computational experience linked to a real case from the automotive industry.

Ergonomic risk minimisation in assembly line balancing

In this work it is presented a variant for the assembly line balancing that considers simultaneously production conditions and labour conditions. Specifically, a new mathematical model is formulated to solve the assembly line balancing problem. The objective of this model is minimising the maximum ergonomic risk, given a specific cycle time and a number of workstations. This affords the evaluation of the ergonomic risk impact on the number of workstations of the line through an application linked to the Nissan plant of engines, located in Barcelona.

Diseño y equilibrado de líneas de montaje minimizando el riesgo ergonómico

Se establece un sistema de medicion del riesgo ergonomico generado por las operaciones requeridas en una linea de montaje. Se formula un modelo matematico para el problema de equilibrado de lineas de ensamblaje, con el objetivo de minimizar el riesgo ergonomico de la linea y considerando el numero de puestos de trabajo, ademas de un conjunto de restricciones de caracter temporal y espacial. Se realiza una aplicacion del modelo mediante una experiencia computacional basada en un caso de estudio de la planta de ensamble de motores de Nissan en Barcelona. El experimento mide el impacto generado por el incremento del numero de puestos de trabajo sobre el incremento de la calidad ergonomica de los mismos en sintonia con la reduccion del riesgo ergonomico de la linea.

Incorporando condiciones laborales a problemas de secuencias en líneas de productos mixtos

Partiendo de una variante de un problema de secuenciacion en lineas de productos mixtos (MMSP-W: Mixed-Model Sequencing Problem with Workload Minimisation), se proponen dos nuevos modelos que incorporan condiciones laborales a los puestos de trabajo de la linea. El primero tiene en cuenta la limitacion de la saturacion de los puestos de trabajo, mientras que el segundo contempla, ademas, la activacion de los operarios a lo largo de la jornada laboral. Se realizan sendas experiencias computacionales, empleando un caso de estudio de la planta de motores de Nissan en Barcelona, con dos propositos: (1) estudiar la repercusion que ocasiona la limitacion de la saturacion sobre la caida de la productividad de la linea, y (2) evaluar la recuperacion de la productividad de la linea, mediante la activacion de los operarios, manteniendo la misma calidad en las condiciones laborales conseguida al limitar la saturacion.